Evolution of the Kondo effect in a quantum dot probed by shot noise.

We measure the current and shot noise in a quantum dot in the Kondo regime to address the nonequilibrium properties of the Kondo effect. By systematically tuning the temperature and gate voltages to define the level positions in the quantum dot, we observe an enhancement of the shot noise as temperature decreases below the Kondo temperature, which indicates that the two-particle scattering process grows as the Kondo state evolves. Below the Kondo temperature, the Fano factor defined at finite temperature is found to exceed the expected value of unity from the noninteracting model, reaching 1.8±0.2.

Nonequilibrium fluctuation relations in a quantum coherent conductor.

We experimentally demonstrate the validity of nonequilibrium fluctuation relations by using a quantum coherent conductor. In equilibrium the fluctuation-dissipation relation leads to the correlation between current and current noise at the conductor, namely, the Johnson-Nyquist relation. When the conductor is voltage biased so that the nonlinear regime is entered, the fluctuation theorem has predicted similar nonequilibrium fluctuation relations, which hold true even when the Onsager-Casmir relations are broken in magnetic fields. Our experiments qualitatively validate the predictions as the first evidence of this theorem in the nonequilibrium quantum regime.

Noise measurement system at electron temperature down to 20 mK with combinations of the low pass filters.

We developed a quantum noise measurement system in a dilution refrigerator by using three kinds of cryogenic low pass filters. One of them is a commercial low pass filter inserted into the noise measurement lines instead of the conventional powder filter, which assures well-defined circuit parameters necessary for the noise measurement at a finite frequency. We checked that this filter gives sufficiently large attenuation up to 20 GHz at room temperature, 77 and 4.2 K. The electron temperature of the mesoscopic device placed in the present system was confirmed to be down to around 20 mK by measuring the thermal noise of the device.

[Beta-lactamase activity and susceptibilities to antibiotics among some species of bacteria isolated from medical institution between December 1999 and February 2000].

We studied the beta-lactamase activity and susceptibilities to antibiotics in 604 strains among 10 species of bacteria isolated from 10 medical institutions in Tottori and Shimane Prefectures between December 1999 and February 2000. beta-Lactamase activity was measured by the nitrocefin test and penicillinase/cephalosporinase activities were measured by acidometry. beta-Lactamase activity was detected in 72.1% of S. aureus, 18.8% of H. influenzae, and 96.3% of M. catarrhalis. Penicillinase/cephalosporinase activities were detected in 17.8%/22.2% of E. coli, 9.7%/0.0% of K. pneumoniae, 18.6%/95.3% of E. cloacae, 12.7%/79.4% of S. marcescens, and 7.1%/31.8% of P. aeruginosa. Three of 72 strains (4.2%) of K. pneumoniae and 5 of 90 strains (5.6%) of E. coli were assessed as ESBL-producing bacteria using the NCCLS proposed screening method based on routine susceptibility testing results. BLNAR were detected in 13 of 69 strains (18.8%) of H. influenzae.